Electrostatographic printers produce images by transferring polymeric toner particles from a photoreceptor to a receiver and fixing the toner particles to the receiver with heat and pressure. Various additives and oils are used to aid the transfer of the particles. Silicone oil is commonly used as a release oil because it is thermally stable and incompatible with the toner particles and other polymers in the printer; unfortunately, however, it tends to spread throughout the machine as prints are made. Release oil spread is exacerbated by duplex printing, which entails the application of images to both sides of a receiver sheet. Oil provided to the receiver during application of the first image on one side of a receiver is carried into the printer on the paper transport web in the course of applying the second image to the opposite side, leading to objectionable image artifacts such as non-uniform density and differences in gloss. Details of fuser oil application are given in U.S. Pat. Nos. 5,157,445 and 5,512,409, the disclosures of which are incorporated herein by reference.
Ink-jet printers produce images by ejecting droplets of ink onto receivers that absorb ink. Porous coatings of inorganic particles on the receivers improve the image quality by, for example, causing more rapid drying of the ink, reducing image spread, and producing more uniform ink coverage. Silica and alumina particles incorporated into binder polymers are used for coatings on paper and coatings on clear plastics such as polyethylene terephthalate sheets. While larger particles can be used to produce opaque coatings on paper substrates, smaller particles are required for coatings that are transparent in a binder, which is also desirably transparent and colorless. Microporous ink-jet recording elements prepared using psuedo-boehmite in organic polymer matrices are described in, for example, U.S. Pat. Nos. 5,723,211; 5,605,750; 5,085,698; 4,879,166; and 4,780,356, the disclosures of which are incorporated herein by reference.
Pseudo-boehmite coatings have also been applied to the photoreceptors used in electrophotographic printing. U.S. Pat. No. 5,693,442, the disclosure of which is incorporated herein by reference, describes the incorporation of a nickel metallized dye into an overcoat of pseudo-boehmite to act as a filter to protect the light sensitive element. The inorganic particles and 5 wt. % of the metallized dye in a poly(vinylpyrrolidone) binder form a transparent layer that can be charged under a corona charger and discharged by exposure to actinide radiation.
The mitigation of objectionable image artifacts such as non-uniform density and differences in gloss that result from the spread of release oil from an imaged receiver into the reproduction apparatus, particularly during a duplex printing process, is provided by the present invention.